When merging a pull request on the GitHub web client, the suggested commit message (at least in the case of a squash commit, which we always use) will automatically include the number of the PR in parentheses, like so:
Update project files (#123)
However, when merging using this extension, the first line of the commit message will look like this:
Update project files
You can still edit it, but the number has to be added manually. I feel like this used to be the case - which is why I had half a mind to make this a bug report, not a feature request - but in any case, I'd prefer it if the extension behaved like the site.